US 8,715,526 B2 · Assignee: JX Nippon Oil & Energy Corporation · Inventors: Kitai; Toru et al.
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The fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention comprises 100 parts by mass of a fully-aromatic thermotropic liquid crystal polyester; and 50 to 150 parts by mass of titanium oxide, wherein the fully-aromatic thermotropic liquid crystal polyester comprises a repeating structural unit represented by the following formula (1), a repeating structural unit represented by the following formula (2), and a repeating structural unit represented by the following formula (3), and comprises 65 mole % to 78 mole % of the repeating structural unit represented by the formula (1). ##STR00001## wherein X and Y each represent a divalent group having an aromatic ring.
In an LED (light-emitting diode) light-emitting apparatus, a reflector (white reflective frame) is provided around an LED device in order to increase the light utilization rate of the LED. As molding materials for LED reflectors, various liquid crystal polyester resin compositions in which a liquid crystal polyester excellent in heat resistance and a white pigment, such as titanium oxide, are blended have been proposed (for example, see the following Patent Literatures 1 to 5).
Ask Claude for concept sketches based only on the patent's text. They are not part of the patent.
What the patent claimed, word for word. All of it is now free to use.
The present invention relates to a fully-aromatic thermotropic liquid crystal polyester resin composition, and a molded object and an LED reflector thereof.
In an LED (light-emitting diode) light-emitting apparatus, a reflector (white reflective frame) is provided around an LED device in order to increase the light utilization rate of the LED. As molding materials for LED reflectors, various liquid crystal polyester resin compositions in which a liquid crystal polyester excellent in heat resistance and a white pigment, such as titanium oxide, are blended have been proposed (for example, see the following Patent Literatures 1 to 5).
Patent Literature
Patent Literature 1: Japanese Examined Patent Application Publication No. 06-38520 Patent Literature 2: Japanese Patent Application Laid-Open Publication No. 2004-256673 Patent Literature 3: Japanese Patent Application Laid-Open Publication No. 2004-277539 Patent Literature 4: Japanese Patent Application Laid-Open Publication No. 2007-254669 Patent Literature 5: Japanese Patent Application Laid-Open Publication No. 2009-256627
Technical Problem
But, a problem of LED reflectors formed of the above conventional liquid crystal polyester resin compositions is that a reflector surface is easily discolored by the light of the LED, and thus, the light reflectance of the reflector decreases, and LED brightness decrease (decrease in light extraction efficiency) occurs.
In recent years, the power of LEDs has increased, and there has been a tendency that light energy that reflectors receive increases. Therefore, for LED reflectors formed of liquid crystal polyester resin compositions, there is a possibility that the above discoloration problem becomes serious.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a fully-aromatic thermotropic liquid crystal polyester resin composition that can produce a molded object which has sufficient light reflectance and in which discoloration due to light is little and light reflectance is less likely to decrease, and a molded object and an LED reflector thereof.
Solution to Problem
In order to solve the above problem, the present inventors have studied diligently, and, as a result, found that a resin composition comprising a fully-aromatic thermotropic liquid crystal polyester containing p-hydroxybenzoic acid (HBA) as a constituent and having a particular repeating structural unit, and titanium oxide particles in a particular amount with respect to this liquid crystal polyester, in which the content of the above HBA in the liquid crystal polyester is set in a particular range, can form a molded object having sufficient light reflectance, and in the molded object, a decrease in light reflectance is smaller than that of conventional ones also after a predetermined light irradiation test. In addition, the present inventors have also found that in a resin composition comprising a fully-aromatic thermotropic liquid crystal polyester obtained by reacting the above BBA, a dicarboxylic acid compound, and a diol compound, and titanium oxide particles in a particular amount with respect to this liquid crystal polyester, by setting the content of the above HBA in the liquid crystal polyester in a particular range and further containing a particular amount of a particular diol compound in the liquid crystal polyester, a molded object having sufficient light reflectance can be formed, and in the molded object, a decrease in light reflectance is smaller than that of conventional ones also after a predetermined light irradiation test. Based on these findings, the present inventors have completed the present invention.
The fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention comprises 100 parts by mass of a fully-aromatic thermotropic liquid crystal polyester; and 50 to 150 parts by mass of titanium oxide, wherein the fully-aromatic thermotropic liquid crystal polyester comprises a repeating structural unit represented by the following formula (1), a repeating structural unit represented by the following formula (2), and a repeating structural unit represented by the following formula (3), and comprises 65 mole % to 78 mole % of the repeating structural unit represented by the formula (1).
##STR00002## wherein X and Y each represent a divalent group having an aromatic ring.
According to the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention, by having the above configuration, a molded object which has sufficient light reflectance and in which discoloration due to light is little and light reflectance is less likely to decrease can be obtained. The present inventors consider that a reason why such an effect is obtained is that by setting the content of the structural unit represented by the above formula
to the above lower limit value or more, the content of the structural units represented by the above formulas
and
that are considered to be a cause of discoloration due to light irradiation can be set relatively small, and on the other hand, by setting the content of the structural unit represented by the above formula
to the above upper limit value or less, the compounding and molding processing, such as injection molding, of the composition are sufficiently possible.
In terms of ensuring the strength, durability, solder heat resistance, and the like of a molded object, a resin composition is required to have sufficiently high mechanical properties, such as flexural modulus, and distortion temperature under load (DTUL), and particularly, in order to ensure heat resistance capable of withstanding solder reflow, the DTUL is preferably 200.degree. C. or more, further preferably 220.degree. C. or more, and the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention can have such heat resistance and mechanical properties.
In the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention, discoloration is less likely to proceed also for light where wavelength is 480 nm, and the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention can have excellent heat resistance capable of withstanding solder reflow, and is preferable, for example, as a material for forming a reflector used for a white LED having a high power of 1 W or more.
In terms of heat resistance and molding processability, it is preferable that the repeating structural unit represented by the above formula
is a residue of terephthalic acid and/or isophthalic acid, and the repeating structural unit represented by the above formula
is a residue of 4,4'-dihydroxybiphenyl.
It is preferable that the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention comprises at least 0.5 mole % to 17.5 mole % of a repeating structural unit represented by the following formula (3-1) as the repeating structural unit represented by the above formula (3).
##STR00003## wherein L.sup.3 represents a divalent hydrocarbon group, --SO.sub.2--, or --CO--.
According to this fully-aromatic thermotropic liquid crystal polyester resin composition, by having the above configuration, a molded object which has sufficient light reflectance and in which discoloration due to light is little and light reflectance is less likely to decrease can be obtained. The present inventors consider that a reason why such an effect is obtained is that by setting the content of the structural unit represented by the above formula
in the above range and setting the structural unit represented by the above formula (3-1) in the above range, the content of the structural unit that is considered to be a cause of discoloration due to light irradiation, of the structural units represented by the above formulas
and (3), can be set relatively small while the compounding and molding processing, such as injection molding, of the composition are made sufficiently possible.
In addition, in terms of heat resistance and molding processability, it is preferable that the above fully-aromatic thermotropic liquid crystal polyester comprises at least 5 mole % to 17.5 mole % of a repeating structural unit represented by the following formula (2-1) as the repeating structural unit represented by the above formula (2).
In addition, in terms of heat resistance and molding processability, it is preferable that the above fully-aromatic thermotropic liquid crystal polyester further comprises 2.5 mole % to 17 mole % of a repeating structural unit represented by the following formula (3-2) as the repeating structural unit represented by the above formula (3).
Further, in terms of further reducing the discoloration of a molded article surface due to light irradiation, it is preferable that the above fully-aromatic thermotropic liquid crystal polyester comprises at least 0.5 mole % to 15 mole % of a repeating structural unit represented by the following formula (3-3) and 2.5 mole % to 17 mole % of a repeating structural unit represented by the following formula (3-2) as the repeating structural unit represented by the above formula (3).
In addition, it is preferable that the fully-aromatic thermotropic liquid crystal polyester of the present invention is obtained by two-stage polymerization of melt polycondensation and solid phase polycondensation. In this case, it is easy to obtain a molded object that is excellent in heat resistance and can withstand solder reflow.
Further, in terms of heat resistance and molding processability, it is preferable that the fully-aromatic thermotropic liquid crystal polyester of the present invention has a melting point of 300.degree. C. or more and 380.degree. C. or less.
In addition, in terms of heat resistance and molding processability, it is preferable that the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention has a complete melting temperature of 300.degree. C. or more and 380.degree. C. or less.
The present invention also provides a molded object comprising the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention described above. The molded object of the present invention can have optical properties which provide sufficient light reflectance and in which discoloration due to light is little and light reflectance is less likely to decrease, and excellent heat resistance and excellent mechanical properties. It is preferable that the molded object of the present invention has a DTUL of 220.degree. C. or more in terms of ensuring heat resistance capable of withstanding solder reflow.
The present invention also provides an LED reflector comprising the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention described above. The LED reflector of the present invention can have optical properties which provide sufficient light reflectance and in which discoloration due to light is little and light reflectance is less likely to decrease, and excellent heat resistance and excellent mechanical properties.
Advantageous Effects of Invention
According to the present invention, it is possible to provide a fully-aromatic thermotropic liquid crystal polyester resin composition that can produce a molded object which has sufficient light reflectance and in which discoloration due to light is little and light reflectance is less likely to decrease, and a molded object and an LED reflector thereof.
The first embodiment of the fully-aromatic thermotropic liquid crystal polyester (hereinafter sometimes simply abbreviated as "LCP") of the present invention comprises a repeating structural unit represented by the following formula (1), a repeating structural unit represented by the following formula (2), and a repeating structural unit represented by the following formula (3), and comprises 65 mole % to 78 mole % of the repeating structural unit represented by the following formula (1). In the LCP according to the present invention, 11 mole % to 17.5 mole % of the repeating structural unit represented by formula
is contained in total, and 11 mole % to 17.5 mole % of the repeating structural unit represented by formula
is contained in total.
##STR00007## wherein X and Y each represent a divalent group having an aromatic ring.
In addition, the second embodiment of the LCP of the present invention comprises 65 mole % to 78 mole % of the repeating structural unit represented by the above formula (1), 11 mole % to 17.5 mole % of the repeating structural unit represented by the above formula
in total, and 11 mole % to 17.5 mole % of the repeating structural unit represented by the above formula
in total, and comprises at least 0.5 mole % to 17.5 mole % of a repeating structural unit represented by the following formula (3-1) as the repeating structural unit represented by the above formula (3).
##STR00008## wherein L.sup.3 represents a divalent hydrocarbon group, --SO.sub.2--, or --CO--.
Examples of the divalent hydrocarbon group include alkanediyl groups having 1 to 3 carbon atoms, and among them, --C(CH.sub.3).sub.2-- or --CH(CH.sub.3)-- is preferable. Two bonds of a benzene ring in formula (3-1) are in a meta or para relationship.
In the LCP according to the present invention, the structural unit represented by formula
may be one or two or more. In addition, in the LCP according to the present invention, the structural unit represented by formula
may be one or two or more. In addition, in the LCP according to the present invention, the content of the repeating structural unit represented by formula (1), the repeating structural unit represented by formula (2), and the repeating structural unit represented by formula
can be set so that their total is 100 mole %, and the content of the structural unit of formula
and the content of the structural unit of formula
are equal.
Examples of the structural units represented by the above formulas
and
include structural units represented by the following formulas (2-A) and (3-A), respectively.
##STR00009## wherein Ar.sup.1 and Ar.sup.2 each represent a divalent aromatic group, X.sup.1 and Y.sup.1 each represent a divalent group having an aromatic ring, and t and v each represent an integer of 0 or 1.
As Ar.sup.1 and Ar.sup.2, a divalent aromatic group represented by the following formula
or
is preferable in terms of heat resistance and molding processability. Two bonds of a benzene ring represented by formula
are in a meta or para relationship.
Examples of X.sup.1 include divalent groups represented by the following formula (6).
##STR00011## wherein L.sup.1 represents a divalent hydrocarbon group, --O--, --S--, --SO--, --SO.sub.2--, or --CO--, and s represents an integer of 0 or 1. Examples of the divalent hydrocarbon group include alkanediyl groups having 1 to 3 carbon atoms, and among them, --C(CH.sub.3).sub.2-- or --CH(CH.sub.3)-- is preferable. Two bonds of a benzene ring in formula
are in a meta or para relationship.
Examples of Y.sup.1 include divalent groups represented by the following formula (7).
##STR00012## wherein L.sup.2 represents a divalent hydrocarbon group, --O--, --S--, --SO--, --SO.sub.2--, or --CO--, and u represents an integer of 0 or 1. Two bonds of a benzene ring in formula
are in a meta or para relationship.
The first embodiment of the LCP according to the present invention can be obtained, for example, by copolymerizing p-hydroxybenzoic acid, an aromatic dicarboxylic acid, and an aromatic dihydroxy compound. A monomer ratio at this time is set so that the repeating structural unit represented by the above formula
in the LCP is 65 mole % to 78 mole %.
The content of the repeating structural unit represented by the above formula
is preferably 65 mole % to 74 mole % in terms of heat resistance and molding processability, and is more preferably 67 mole % to 74 mole % in that discoloration can be further suppressed.
Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and benzophenone-4,4'-dicarboxylic acid. One of these can be used alone, or two or more of these can be used in combination.
In the first embodiment of the LCP according to the present invention, it is preferable to copolymerize terephthalic acid so that 5 mole % to 15 mole % of terephthalic acid is contained in the LCP, in terms of heat resistance and molding processability.
Examples of the aromatic dihydroxy compound include hydroquinone, 4,4'-dihydroxybiphenyl, and 2,6-naphthalenediol. One of these can be used alone, or two or more of these can be used in combination.
In the first embodiment of the LCP according to the present invention, it is preferable to copolymerize 4,4'-dihydroxybiphenyl so that 5 mole % to 17 mole % of 4,4'-dihydroxybiphenyl is contained, in terms of heat resistance and molding processability.
In addition, it is preferable that in the first embodiment of the LCP according to the present invention, the repeating structural unit represented by the above formula
is a residue of terephthalic acid and/or isophthalic acid, and the repeating structural unit represented by the above formula
is a residue of 4,4'-dihydroxybiphenyl, in terms of heat resistance and molding processability.
In the second embodiment of the LCP according to the present invention, the structural unit represented by the above formula (3-1), that is, a structural unit in which Ar.sup.2 in the above formula (3-A) is the divalent aromatic group represented by the above formula (4), v is 1, and Y.sup.1 is the divalent group represented by the above formula (7), and u in the above formula
is 1, and L.sup.2 is a divalent hydrocarbon group, --SO.sub.2--, or --CO--, is contained as an essential structural unit.
It is preferable that the second embodiment of the LCP according to the present invention comprises at least 5 mole % to 17.5 mole % of a repeating structural unit represented by the following formula (2-1) as the repeating structural unit represented by the above formula (2), in terms of heat resistance and molding processability. This structural unit can be introduced into the LCP by using terephthalic acid as a copolymerization monomer for preparing LCP.
In addition, it is preferable that the second embodiment of the LCP according to the present invention further comprises 2.5 mole % to 17 mole % of a repeating structural unit represented by the following formula (3-2) as the repeating structural unit represented by the above formula (3), in terms of heat resistance and molding processability. This structural unit can be introduced into the LCP by using 4,4'-biphenol as a copolymerization monomer for preparing LCP.
Further, it is preferable that in the second embodiment of the LCP according to the present invention, the above fully-aromatic thermotropic liquid crystal polyester comprises at least 0.5 mole % to 15 mole % of a repeating structural unit represented by the following formula (3-3) and 2.5 mole % to 17 mole % of a repeating structural unit represented by the following formula (3-2) as the repeating structural unit represented by the above formula (3), in terms of further reducing the discoloration of a molded article surface due to light irradiation. These structural units can be introduced into the LCP by using 4,4'-dihydroxybenzophenone and 4,4'-biphenol as copolymerization monomers for preparing LCP.
The second embodiment of the LCP according to the present invention can be obtained, for example, by copolymerizing p-hydroxybenzoic acid, an aromatic dicarboxylic acid, and an aromatic dihydroxy compound. A monomer ratio at this time is set so that the repeating structural unit represented by the above formula
in the LCP is 65 mole % to 78 mole % and the repeating structural unit represented by the above formula (3-1) in the LCP is 0.5 mole % to 17.5 mole %.
The content of the repeating structural unit represented by the above formula
is preferably 65 mole % to 78 mole % in terms of heat resistance and molding processability.
Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid. One of these can be used alone, or two or more of these can be used in combination.
In the second embodiment, it is preferable to copolymerize terephthalic acid so that 5 mole % to 17.5 mole % of terephthalic acid is contained in the LCP, in terms of heat resistance and molding processability.
Examples of the aromatic dihydroxy compound include 4,4'-dihydroxybenzophenone, bisphenol-S, bisphenol-A, hydroquinone, 4,4'-dihydroxybiphenyl(4,4'-biphenol), and 2,6-naphthalenediol. One of these can be used alone, or two or more of these can be used in combination.
In the second embodiment, it is preferable to copolymerize one or more of 4,4'-dihydroxybenzophenone, bisphenol-S, and bisphenol-A so that 0.5 mole % to 17.5 mole %, more preferably 0.5 mole % to 15 mole %, of one or more of 4,4'-dihydroxybenzophenone, bisphenol-S, and bisphenol-A are contained in total, for the purpose of introducing the repeating structural unit represented by the above formula (3-1).
In addition, in the second embodiment, it is preferable to use 4,4'-dihydroxybiphenyl and 4,4'-dihydroxybenzophenone in combination and copolymerize 4,4'-dihydroxybiphenyl and 4,4'-dihydroxybenzophenone so that 2.5 mole % to 17 mole % of 4,4'-dihydroxybiphenyl and 0.5 mole % to 15 mole % of 4,4'-dihydroxybenzophenone, more preferably 2.5 mole % to 14.5 mole % of 4,4'-dihydroxybiphenyl and 3 mole % to 15 mole % of 4,4'-dihydroxybenzophenone, are contained, in terms of heat resistance and molding processability.
Examples of a method for preparing the LCP according to the present invention include a method of charging p-hydroxybenzoic acid, the above aromatic dicarboxylic acid, and the above aromatic dihydroxy compound in a proportion in which a monomer composition in the LCP is 65 mole % to 78 mole %, 11 mole % to 17.5 mole %, and 11 mole % to 17.5 mole %, respectively, to perform melt polycondensation.
In the production of the LCP according to the present invention, in order to shorten melt polycondensation time and reduce the effect of a thermal history during steps, it is preferable to perform melt polycondensation after previously acetylating the hydroxyl groups of the above monomers. Further, in order to simplify the steps, it is preferable that the acetylation is performed by feeding acetic anhydride to the monomers in a reaction vessel, and it is preferable to perform this acetylation step using the same reaction vessel as in the melt polycondensation step. In other words, it is preferable to perform the acetylation reaction of the raw material monomers with acetic anhydride in a reaction vessel and, after the completion of the reaction, increase temperature to transition to a polycondensation reaction. In addition, it is preferable that acetic anhydride is fed so that the excessive amount of acetic anhydride is 1 to 10 mole % with respect to the number of moles of the hydroxyl groups of the monomers. If the excessive amount of acetic anhydride is less than 1 mole %, there is a tendency that a reaction rate is slow and the LCP is colored, and if the excessive amount of acetic anhydride is more than 10 mole %, there is a tendency that the LCP is colored by the effect of residual acetic anhydride.
The acetylated monomers can be subjected to a melt polycondensation reaction with an acetic acid removal reaction. As the reaction vessel, it is preferable to use a reaction vessel equipped with monomer feed means, acetic acid discharge means, molten polyester extraction means, and stirring means. Such a reaction vessel (polycondensation apparatus) can be appropriately selected from publicly known ones. Polymerization temperature is preferably 150.degree. C. to 350.degree. C. It is preferable to, after the completion of the acetylation reaction, increase temperature to polymerization initiation temperature to initiate polycondensation and increase the temperature in the range of 0.1.degree. C./min to 2.degree. C./min to 280 to 350.degree. C. as final temperature. It is preferable to increase polycondensation temperature correspondingly to the fact that the melting temperature of a produced polymer increases with the progress of polycondensation, in this manner. In the polycondensation reaction, catalysts publicly known as polycondensation catalysts for polyesters can be used. Examples of the catalysts include metal catalysts, such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, and potassium acetate, and organic compound catalysts, such as N-methylimidazole.
In the melt polycondensation, when the flow point reaches 200.degree. C. or more, preferably 220.degree. C. to 330.degree. C., a fully-aromatic thermotropic liquid crystal polyester having a low degree of polymerization is extracted from the polymerization vessel in a molten state, fed to a cooling machine, such as a steel belt or a drum cooler, and cooled and solidified.
Then, the solidified fully-aromatic thermotropic liquid crystal polyester having a low degree of polymerization is ground to a size suitable for the subsequent solid phase polycondensation reaction. A grinding method is not particularly limited, and preferable examples include methods using apparatuses such as impact type grinding machines, such as Feather Mill, Victory Mill, Kolloplex, Pulverizer, Contraplex, Scroll Mill, and ACM Pulverizer manufactured by Hosokawa Micron Corporation, and Roll Granulator, which is a cracking type grinding machine manufactured by MATSUBO Corporation. The grinding method is particularly preferably a method using Feather Mill manufactured by Hosokawa Micron Corporation. In the present invention, there is no particular limitation on the particle diameter of a ground product, and the particle diameter is preferably in the range of passing through 4 mesh to not passing through 2000 mesh with an industrial sieve (Tyler mesh), further preferably in the range of 5 mesh to 2000 mesh (0.01 to 4 mm), and most preferably in the range of 9 mesh to 1-450 mesh (0.02 to 2 mm).
Then, the ground product obtained in the grinding step is subjected to a solid phase polycondensation step to perform solid phase polycondensation. There is no particular limitation on an apparatus used for the solid phase polycondensation step, and its operation conditions, and publicly known apparatuses and methods can be used.
It is preferable that the LCP according to the present invention is obtained by two-stage polymerization of melt polycondensation and solid phase polycondensation, in that one in which coloration is little is obtained.
It is preferable that the LCP according to the present invention has a melting point of 300.degree. C. or more and 380.degree. C. or less, in terms of heat resistance and molding processability.
It is preferable that the content of the fully-aromatic thermotropic liquid crystal polyester in the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention is 30 to 80% by mass based on the total amount of the resin composition.
Titanium oxide used in the present invention means particles of TiO.sub.2 and is one widely used as a white pigment. The titanium oxide particles are preferably rutile type titanium oxide particles, which are stable even at high temperature and have large light hiding power. In addition, the titanium oxide particles are preferably those in which primary (number average) particle diameter is 0.1 to 0.5 .mu.M, more preferably 0.2 to 0.3 .mu.m. When the primary number average particle diameter is in this range, light scattering efficiency is high, the light reflectance of the molded surface of a molded object increases, and one having high brightness is easily obtained. If the particle diameter is less than 0.1 .mu.m, a result is that a light scattering effect is small, and the brightness of the molded surface decreases, and if the particle diameter is more than 0.5 .mu.m, there is a tendency that the dispersibility of the titanium oxide particles in the resin (LCP) worsens, and a case where a filling amount is increased is not preferable in terms of workability. For the titanium oxide particles, commercial products, for example, SR-1 (trade name, manufactured by Sakai Chemical Industry Co., Ltd.), can be used.
The content of the titanium oxide particles in the resin composition is 50 to 150 parts by mass with respect to 100 parts by mass of the fully-aromatic thermotropic liquid crystal polyester, and is preferably 70 to 130 parts by mass. If the content of the titanium oxide particles is less than the above lower limit value, there is a tendency that a sufficient degree of whiteness is not obtained, and on the other hand, if the content of the titanium oxide particles is more than the above upper limit value, the heat resistance of a molded object obtained by injection-molding the resin composition is insufficient, and a possibility that blistering occurs when the molded object is heat treated increases, and therefore, there is a tendency that it is difficult to use the resin composition as reflector member applications, which require a good molded surface.
A white pigment other than titanium oxide particles can be blended in the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention in a range in which the effect of the invention of this application is not impaired. Examples of the white pigment include zinc oxide and lead carbonate.
It is preferable that the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention further contains a fibrous inorganic filler. Examples of the fibrous inorganic filler include glass fibers, alumina fibers, and wollastonite.
As the glass fibers, those used as general resin reinforcement materials, such as chopped strands and milled fibers, can be preferably used, and chopped strands are preferable. The fiber length of the glass fiber used is 100 .mu.m to 10 mm, preferably 200 .mu.m to 5 mm, and further preferably 0.1 mm to 3 mm, in terms of number average length. The thickness of the glass fiber is preferably a number average diameter of 5 to 20 .mu.m in terms of flowability during injection molding, and is further preferably a number average diameter of 7 to 15 .mu.m. Preferable specific examples of the glass fibers include "PX-1" (number average fiber diameter: 10 .mu.m, number average fiber length: 3 mm) manufactured by OWENS CORNING JAPAN LTD.
Further, an inorganic filler, for example, talc, mica, or silica, can be blended in the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention in a range in which the effect of the invention of this application is not impaired, to provide desired properties.
When the resin composition of the present invention comprises the fibrous inorganic filler, it is preferable that its content is 5 to 50 parts by mass with respect to 100 parts by mass of the fully-aromatic thermotropic liquid crystal polyester. If the content of the fibrous inorganic filler is less than the lower limit value, the effect of reinforcement is less likely to be obtained, and if the content of the fibrous inorganic filler is more than the upper limit value, there is a tendency that the productivity and molding processability of the resin composition decrease significantly.
One or two or more of various additives can be blended in the resin composition of the present invention in a range in which the object of the present invention is not impaired. Examples of the additives include usual additives, such as powdery or acicular inorganic fillers, such as silica, talc, and potassium titanate whiskers, antioxidants and heat stabilizers (for example, hindered phenols, hydroquinone, phosphites and substitution products thereof), ultraviolet-absorbing agents (for example, resorcinol, salicylate, benzotriazole, and benzophenone), lubricants and release agents (montanic acid and salts, esters, and half esters thereof, stearyl alcohol, stearamide, polyethylene wax, and the like), plasticizers, antistatic agents, and flame retardants, and other thermoplastic resins. These additives can be added to provide desired properties to the resin composition.
It is preferable that the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention has a complete melting temperature of 300.degree. C. or more and 380.degree. C. or less. Here, the complete melting temperature of the resin composition means change temperature from the crystalline phase to the liquid crystalline phase of the resin composition as described in Japanese Patent Application Laid-Open Publication No. 10-95839, and this change temperature can be obtained by an apparent viscosity-temperature curve. If the complete melting temperature is less than 300.degree. C., the heat resistance of a molded object of the fully-aromatic thermotropic liquid crystal polyester resin composition may be insufficient, which is not preferable. On the other hand, if the complete melting temperature is more than 380.degree. C., the molding processing temperature of the fully-aromatic thermotropic liquid crystal polyester resin composition is high, and therefore, a molded object surface may be discolored by excessive heat.
The fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention described above can be subjected to molding processing at 380.degree. C. or less and can form a molded object which sufficiently satisfies a degree of whiteness and heat resistance and in which discoloration due to light irradiation is less than that of conventional liquid crystal polyester resin compositions.
The fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention can be preferably used as a resin composition for molding an LED reflector.
In the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention, light reflectance on the molded surface of a molded object obtained by injection molding, for light having a wavelength of 480 nm, is preferably 70% or more, more preferably 80% or more, and further preferably 85% or more. More specifically, the 480 nm wave light reflectance (relative reflectance when the diffuse reflectance of a standard white plate of barium sulfate is taken as 100%) of the surface of a 3 mm thick flat plate test piece obtained by injection molding under standard conditions using a standard mold is preferably 70% or more, more preferably 80% or more, and further preferably 85% or more. If such reflectance is less than the lower limit, there is a tendency that the molded object obtained from the resin composition cannot satisfy light reflection performance required as a reflector.
Further, it is preferable that in the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention, a decrease in light reflectance on the molded surface of a molded object obtained by injection molding, after 480 nm light irradiation, is small. Specifically, a difference between light reflectance before light irradiation and light reflectance before and after 500 hour light irradiation is preferably 15% or less, more preferably 10% or less. In addition, the above light reflectance before and after 500 hour light irradiation is preferably 70% or more.
The fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention can be obtained by melting and kneading the above-described components (the fully-aromatic thermotropic liquid crystal polyester, the titanium oxide particles, and the fibrous inorganic filler as required). As an apparatus for melting and kneading, twin screw kneading machines can be used. More preferably, continuous extrusion type twin screw kneading machines having a pair of double thread screws can be used, and among them, a corotating type that allows the uniform dispersion of the filler by having a turning mechanism is preferable. When one which has a cylinder diameter of 40 mm .phi. or more with a large barrel-screw gap making the entry of the filler easy, in which a gap between screws is large and an intermeshing rate is 1.45 or more, and in which the filler can be fed from the middle of a cylinder is used, the resin composition of the present invention can efficiently be obtained. In addition, it is preferable to use one having equipment for feeding at least part of glass fibers to the middle of a cylinder.
It is preferable that the fully-aromatic thermotropic liquid crystal polyester and the titanium oxide particles are mixed using publicly known solid mixing equipment, for example, a ribbon blender, a tumbler blender, or a Henschel mixer, and the mixture is dried by a hot air dryer, a reduced pressure dryer, or the like as required, and fed from the hopper of a twin screw kneading machine.
In the production of a resin composition containing a fibrous inorganic filler, such as glass fibers, it is preferable to feed at least part of glass fibers to be blended, from the middle of the cylinder of a twin screw kneading machine (so-called side feed). Thus, there is a tendency that the mechanical strength of the welded portion of a molded object prepared by injection-molding the obtained resin composition improves more than in a case where all glass fibers are fed from a hopper together with other raw materials (so-called top feed). The proportion of the glass fibers for side feed, of the total amount of the glass fibers to be blended, is preferably 50% or more, most preferably 100%. If the proportion of the glass fibers for side feed is less than the above lower limit, there is a tendency that compounding (blending and mixing) is difficult and a homogeneous resin composition cannot be obtained.
The molded object of the present invention is prepared by molding the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention described above. Examples of a molding method include injection molding, extrusion molding, and press molding, and injection molding using an injection molding machine is preferable in terms of the ease of molding, mass productivity, cost, and the like. For example, by injection-molding the fully-aromatic thermotropic liquid crystal polyester resin composition of the present invention that is pelletized and using the surface of the injection-molded article as a reflective surface, an LED reflector that is excellent in light reflectance and heat resistance and is less likely to be discolored by light can be obtained. Particularly, the resin composition of the present invention is less likely to be discolored than conventional liquid crystal polyester resin compositions even if it receives light in ultraviolet light to visible light regions, and therefore, an LED reflector also suitable for a high power LED can be obtained.
In the LED reflector of the present invention, light reflectance on a surface for light having a wavelength of 480 nm is preferably 70% or more, more preferably 80% or more, and further preferably 85% or more.
The present invention will be more specifically described below by Examples, but the present invention is not limited to the following Examples.
First Examples and Comparative Examples
Production of Fully-Aromatic Thermotropic Liquid Crystal Polyesters
The description continues in the full USPTO document.
About 6,191 words. The USPTO PDF has it with every drawing.
Fees are due 3.5, 7.5 and 11.5 years after grant. This patent expired on May 6, 2026, so the fee marked "not paid" was the one that went unpaid.
FULLY-AROMATIC THERMOTROPIC LIQUID CRYSTAL POLYESTER RESIN COMPOSITION, MOLDED OBJECT, AND LED REFLECTOR
Filed Mar 2011 · published Mar 2013Fully-aromatic thermotropic liquid crystal polyester resin composition, molded object, and LED reflector
Filed Mar 2011 · granted May 2014Earlier publications, parents and continuations. None of them can still be enforced, or this patent would not be listed.
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